Reflective eyepiece optical system and head-mounted near-to-eye display device

ABSTRACT

The present invention relates to a reflective eyepiece optical system and a head-mounted near-to-eye display device. The system includes: a first optical element and a second optical element arranged successively in an incident direction of an optical axis of human eyes, and a first lens group located on an optical axis of a miniature image displayer. The first optical element is used for transmitting and reflecting an image light from the miniature image displayer. The second optical element includes an optical reflection surface. The first optical element reflects the image light refracted by the first lens group to the second optical element, and then transmits the image light reflected by the second optical element to the human eyes.

CROSS-REFERENCE TO RELATED APPLICATIONS

The application claims priority to Chinese patent application No.202110879521.9, filed on Aug. 2, 2021, the entire contents of which areincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to the field of optical technology, andmore particularly, to a reflective eyepiece optical system and ahead-mounted near-to-eye display device.

BACKGROUND

With the development of electronic devices to ultra-miniaturization,head-mounted display devices and products are constantly emerging inmilitary, industrial, medical, educational, consumption and otherfields, and in a typical wearable computing architecture, a head-mounteddisplay device is a key component. The head-mounted display devicedirects the video image light emitted from a miniature image displayer(e.g., a transmissive or reflective liquid crystal displayer, an organicelectroluminescent element, or a DMD device) to the pupil of a user byoptical technology to implement virtual magnified images in the near-eyerange of the user, so as to provide the user with intuitive and visualimages, video, and text information. The eyepiece optical system is thecore of the head-mounted display device, which realizes the function ofdisplaying a miniature image in front of human eyes to form a virtualmagnified image.

The head-mounted display device develops in the direction of compactsize, light weight, convenient wearing, and load reduction. Meanwhile, alarge field-of-view angle and visual comfort experience have graduallybecome key factors to evaluate the quality of the head-mounted displaydevice. The large field-of-view angle determines a visual experienceeffect of high liveness, and high image quality and low distortiondetermine the comfort of visual experience. To meet these requirements,the eyepiece optical system should try its best to achieve such indexesas a large field-of-view angle, high image resolution, low distortion,small field curvature, and a small volume. It is a great challenge forsystem design and aberrations optimization to meet the above opticalproperties at the same time.

In Patent Document 1 (Chinese Patent Publication No. CN101915992A).Patent Document 2 (Chinese Patent Publication No. CN211698430U), PatentDocument 3 (Chinese Patent Publication No. CN106662678A), and PatentDocument 4 (Chinese Patent Publication No. CN105229514A), a reflectiveoptical system utilizing a combination of conventional optical sphericalsurfaces and even-order aspherical surfaces is provided respectively,wherein Patent Document 1 adopts a relay scheme, but this scheme adoptsa free-form surface reflection means, which greatly increases thedifficulty of realizing the entire optical system; the optical systemsin the Patent Document 2, Patent Document 3, and Patent Document 4 usereflective optical systems, but the basic optical structures varygreatly from one to another due to different application fields, such asin terms of a matching relationship between a lens face shape and a gapbetween the lenses.

Patent Document 5 (Chinese Patent Publication No. CN207081891U) andPatent Document 6 (Chinese Patent Publication No. CN108604007A) providean eyepiece optical system that adopts a reflex means, which ensureshigh-quality imaging; however, its optical structure is often limited tosingle lens reflection, thereby greatly limiting a performance ratio ofthe entire optical structure.

To sum up, the existing optical structures not only have problems suchas heavyweight, small field-of-view angle, and insufficient opticalperformance, but also have problems such as difficulty in processing andmass production due to the difficulty of implementation.

SUMMARY

The technical problem to be solved by the present invention is that theexisting optical structure has the problems of heavy weight, low imagequality, distortion, insufficient field-of-view angle, and difficulty inmass production. Aiming at the above defects of the prior art, areflective eyepiece optical system and a head-mounted near-to-eyedisplay device are provided.

The technical solutions adopted in the present invention to solve thetechnical problem thereof are as follows: constructing a reflectiveeyepiece optical system, including: a first optical element and a secondoptical element arranged successively in an incident direction of anoptical axis of human eyes, and a first lens group located on an opticalaxis of a miniature image displayer, the first optical element is usedfor transmitting and reflecting an image light from the miniature imagedisplayer; the second optical element includes an optical reflectionsurface, and the optical reflection surface is concave to the humaneyes; the first optical element reflects the image light refracted bythe first lens group to the second optical element, and then transmitsthe image light reflected by the second optical element to the humaneyes;

an effective focal length of the eyepiece optical system is f_(w), aneffective focal length of the first lens group is f₁, an effective focallength of the second optical element is f₂, and f_(w), f₁, and f₂satisfy the following relations (1) and (2):f ₁ /f _(w)<−0.47  (1);−2.53<f ₂ /f _(w)<−0.64  (2);

the first lens group includes a first sub-lens group, a second sub-lensgroup, a third sub-lens group, and a fourth sub-lens group arrangedcoaxially and successively along the optical axis direction from a humaneye viewing side to the miniature image displayer side; effective focallengths of the first sub-lens group, the second sub-lens group, and thethird sub-lens group are a combination of positive, negative andpositive; the effective focal length of the first sub-lens group is f₁₁,the effective focal length of the second sub-lens group is f₁₂, theeffective focal length of the third sub-lens group is f₁₃, and f₁₁, f₁₂,f₁₃, and f₁ satisfy the following relations (3), (4), and (5):0.19<f ₁₁ /f ₁  (3);f ₁₂ /f ₁<−0.019  (4);0.019<f ₁₃ /f ₃  (5).

Further, a distance along the optical axis between the first opticalelement and the second optical element is d₁, a distance along theoptical axis between the first optical element and the first lens groupis d₂, and d₁ and d₂ satisfy the following relation (6):0.82<d ₂ /d ₁  (6).

Further, a maximum effective optical aperture of the second opticalelement is φ₂, which satisfies the following relation (7):φ₂<70 mm  (7).

Further, the effective focal length f₁₁ of the first sub-lens group, theeffective focal length f₁₂ of the second sub-lens group, the effectivefocal length f₁₃ of the third sub-lens group, and the effective focallength f₁ of the first lens group further satisfy the followingrelations (8). (9), and (10):0.78<f ₁₁ /f ₁<1.06  (8);−1.16<f ₁₂ /f ₁<−0.90  (9);1.38<f ₁₃ /f ₁<3.6  (10).

Further, the first sub-lens group is composed of one lens; wherein, thefirst sub-lens group includes a first lens; and the first lens is apositive lens.

Further, the first sub-lens group is composed of two lenses, which arerespectively a first lens distant from the miniature image displayerside and a second lens proximate to the miniature image displayer side;both the first lens and the second lens are positive lenses.

Further, an effective focal length of the first lens is f₁₁₁, and theeffective focal length of the first sub-lens group is f₁₁, the f₁₁₁ andf₁₁ satisfy the following relation (11),0.10<|f ₁₁₁ /f ₁₁|  (11).

Further, an optical surface of the first lens proximate to the human eyeside is convex to the human eyes.

Further, the second sub-lens group is composed of one lens, wherein thesecond sub-lens group includes a third lens adjacent to the firstsub-lens group; the third lens is a negative lens; an effective focallength of the third lens is f₁₂₁, and f₁₂₁ satisfies the followingrelation (12):f ₁₂₁<−5.38  (12).

Further, the third sub-lens group is composed of one lens, wherein thethird sub-lens group includes a fourth lens adjacent to the secondsub-lens group; the fourth lens is a positive lens; an effective focallength of the fourth lens is f₁₃₁, and f₁₃₁ satisfies the followingrelation (13):8.82<f ₁₃₁  (13).

Further, the fourth sub-lens group is composed of one lens, wherein thefourth sub-lens group includes a fifth lens adjacent to the thirdsub-lens group; an optical surface of the fifth lens proximate to theminiature image displayer side is concave to the miniature imagedisplayer; an effective focal length of the fifth lens is f₁₄₁, and f₁₄₁satisfies the following relation (14):2.15<|f ₁₄₁ /f ₁|  (14).

Further, the fifth lens and the miniature image displayer are movabletogether along the optical axis, for adjusting an equivalent visualvirtual image distance of the eyepiece optical system.

Further, the first lens group includes one or more even-order asphericalface shapes; two optical surfaces of the fifth lens are both even-orderaspherical face shapes; and two optical surfaces of the second opticalelement are both even-order aspherical face shapes.

Further, the even-order aspherical face shape satisfies the followingrelation (15):

$\begin{matrix}{z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {\alpha_{2}r^{2}} + {\alpha_{4}r^{4}} + {\alpha_{6}r^{6}} + {\ldots.}}} & (15)\end{matrix}$

Further, the first optical element is a planar transflective opticalelement; a reflectivity of the first optical element is Re₁, and Re₁satisfies the following relation (16):20%<Re ₁<80%  (16).

Further, the second optical element includes two coaxial opticalsurfaces of the same face shape.

Further, a reflectivity of the optical reflection surface is Re₂, andRe₂ satisfies the following relation (17):20%<Re ₂  (17).

Further, an angle of optical axis between the first lens group and thesecond optical element is λ₁, and λ₁ satisfies the following relation(18):55°<λ₁<120°  (18).

Further, the eyepiece optical system further includes a planarreflective optical element located between the first lens group and thefirst optical element; the planar reflective optical element reflectsthe image light refracted by the first lens group to the first opticalelement, the first optical element reflects the image light to thesecond optical element, and then transmits the image light reflected bythe second optical element to the human eyes;

an included angle between the first lens group and the first opticalelement is λ₂, and λ₂ satisfies the following relation (19):60°≤λ₂≤180°  (19).

Further, the material of the second optical element is an opticalplastic material.

The present application provides a head-mounted near-to-eye displaydevice, including a miniature image displayer, and further including thereflective eyepiece optical system according to any one of the aboveitems; wherein the eyepiece optical system is located between the humaneyes and the miniature image displayer.

Further, the miniature image displayer is an organic electroluminescentdevice.

Further, the head-mounted near-to-eye display device includes twoidentical reflective eyepiece optical systems.

The present invention has following beneficial effects: the firstoptical element has transmission and reflection properties, the secondoptical element includes a reflection surface, the eyepiece opticalsystem composed of the first lens group, the first optical element, andthe second optical element is used for effectively folding the opticalpath, which reduces the overall size of the eyepiece optical system andimproves the possibility of subsequent mass production. The first lensgroup includes a first sub-lens group, a second sub-lens group, a thirdsub-lens group, and a fourth sub-lens group. The first sub-lens group,the second sub-lens group, and the third sub-lens group adopt a focallength combination of positive, negative, and positive, and the focallength of the fourth sub-lens group may be positive or negative. On thebasis of miniaturization, cost and weight reduction for the article, theaberrations of the optical system are greatly eliminated, and the basicoptical indicators are also improved, ensuring high image quality andincreasing the size of the picture angle. Therefore, an observer canwatch large images of full frame, high definition and uniform imagequality without any distortion and get visual experience of highliveness via the present invention, which is suitable for near-to-eyedisplays and similar devices thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to illustrate technical solutions of embodiments of the presentinvention or the prior art more clearly, the present invention will befurther illustrated below with reference to accompanying drawings andembodiments. The accompanying drawings described below are merely someembodiments of the present invention, and for those of ordinary skill inthe art, other accompanying drawings can be obtained according to theseaccompanying drawings without creative effort:

FIG. 1 is an optical path structural diagram of a reflective eyepieceoptical system according to a first embodiment of the present invention;

FIG. 2 is a schematic spot diagram of the reflective eyepiece opticalsystem according to the first embodiment of the present invention;

FIG. 3 a is a schematic diagram of a field curvature of the reflectiveeyepiece optical system according to the first embodiment of the presentinvention;

FIG. 3 b is a schematic diagram of a distortion of the reflectiveeyepiece optical system according to the first embodiment of the presentinvention;

FIG. 4 is a plot of an optical modulation transfer function (MTF) of thereflective eyepiece optical system according to the first embodiment ofthe present invention;

FIG. 5 is an optical path structural diagram of a reflective eyepieceoptical system according to a second embodiment of the presentinvention;

FIG. 6 is a schematic spot diagram of the reflective eyepiece opticalsystem according to the second embodiment of the present invention;

FIG. 7 a is a schematic diagram of a field curvature of the reflectiveeyepiece optical system according to the second embodiment of thepresent invention;

FIG. 7 b is a schematic diagram of a distortion of the reflectiveeyepiece optical system according to the second embodiment of thepresent invention;

FIG. 8 is a plot of an optical MTF of the reflective eyepiece opticalsystem according to the second embodiment of the present invention;

FIG. 9 a is a front view of an optical path structure of a reflectiveeyepiece optical system according to a third embodiment of the presentinvention;

FIG. 9 b is a top view of the optical path structure of the reflectiveeyepiece optical system according to the third embodiment of the presentinvention;

FIG. 10 is a schematic spot diagram of the reflective eyepiece opticalsystem according to the third embodiment of the present invention;

FIG. 11 a is a schematic diagram of a field curvature of the reflectiveeyepiece optical system according to the third embodiment of the presentinvention;

FIG. 11 b is a schematic diagram of a distortion of the reflectiveeyepiece optical system according to the third embodiment of the presentinvention;

FIG. 12 is a plot of an optical MTF of the reflective eyepiece opticalsystem according to the third embodiment of the present invention;

FIG. 13 a is a front view of an optical path structure of a reflectiveeyepiece optical system according to a fourth embodiment of the presentinvention;

FIG. 13 b is a top view of the optical path structure of the reflectiveeyepiece optical system according to the fourth embodiment of thepresent invention:

FIG. 14 is a schematic spot diagram of the reflective eyepiece opticalsystem according to the fourth embodiment of the present invention;

FIG. 15 a is a schematic diagram of a field curvature of the reflectiveeyepiece optical system according to the fourth embodiment of thepresent invention;

FIG. 15 b is a schematic diagram of a distortion of the reflectiveeyepiece optical system according to the fourth embodiment of thepresent invention;

FIG. 16 is a plot of an optical MTF of the reflective eyepiece opticalsystem according to the fourth embodiment of the present invention;

FIG. 17 is an optical path structural diagram of a reflective eyepieceoptical system according to a fifth embodiment of the present invention;

FIG. 18 is a schematic spot diagram of the reflective eyepiece opticalsystem according to the fifth embodiment of the present invention;

FIG. 19 a is a schematic diagram of a field curvature of the reflectiveeyepiece optical system according to the fifth embodiment of the presentinvention;

FIG. 19 b is a schematic diagram of a distortion of the reflectiveeyepiece optical system according to the fifth embodiment of the presentinvention; and

FIG. 20 is a plot of an optical MTF of the reflective eyepiece opticalsystem according to the fifth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In order to clarify the objects, technical solutions and advantages ofthe embodiments of the present invention, the following clear andcomplete description will be made for the technical solution in theembodiments of the present invention. Apparently, the describedembodiments are just some rather than all embodiments of the presentinvention. All other embodiments obtained by one of ordinary skill inthe art without any creative effort based on the embodiments disclosedin the present invention fall into the scope of the present invention.

The present invention constructs a reflective eyepiece optical system,including: a first optical element and a second optical element arrangedsuccessively in an incident direction of an optical axis of human eyes,and a first lens group located on an optical axis of a miniature imagedisplayer; the first optical element is used for transmitting andreflecting an image light from the miniature image displayer, the secondoptical element includes an optical reflection surface, and the opticalreflection surface is concave to a human eye viewing direction; thefirst optical element reflects the image light refracted by the firstlens group to the second optical element, and then transmits the imagelight reflected by the second optical element to the human eyes.

An effective focal length of the eyepiece optical system is f_(w), aneffective focal length of the first lens group is f₁, an effective focallength of the second optical element is f₂, and f_(w), f₁, and f₂satisfy the following relations (1) and (2):f ₁ /f _(w)<−0.47  (1);−2.53<f ₂ /f _(w)<−0.64  (2);

wherein, a value of f₁/f_(w) may be −100.57, −56.55, −33.351, −21.131,−10.951, −7.935, −5.815, −3.615, −1.589, −0.47, etc., and a value off₂/f_(w) may be −2.53, −2.521, −2.13, −1.99, −1.55, −1.21, −1.02, −0.98,−0.875, −0.753, −0.659, −0.64, etc.

The first lens group includes a first sub-lens group, a second sub-lensgroup, a third sub-lens group, and a fourth sub-lens group arrangedcoaxially and successively along an optical axis from a human eyeviewing side to the miniature image displayer side; effective focallengths of the first sub-lens group, the second sub-lens group, and thethird sub-lens group are a combination of positive, negative andpositive; the effective focal length of the first sub-lens group is f₁₁,the effective focal length of the second sub-lens group is f₁₂, theeffective focal length of the third sub-lens group is f₁₃, and f₁₁ f₁₂,f₁₃ and f₁ satisfy the following relations (3), (4), and (5):0.19<f ₁₁ /f ₁  (3);f ₁₂ /f ₁<−0.019  (4);0.019<f ₁₃ /f ₁  (5).

wherein, a value of f₁₁/f₁ may be 0.19, 0.20, 0.39, 0.57, 0.77, 0.89,1.35, 3.25, 5.56, 36.1, 54.1, 87.6, etc., a value of f₁₂/f₁ may be−120.43, −100.47, −77.55, −51.25, −45.33, −21.78, −15.13, −10.55, −7.15,−4.14, −0.13, −0.02, −0.019, etc., and a value of f₁₃/f₁ may be 0.019,0.020, 0.139, 1.99, 5.83, 12.13, 22.54, 35.24, 43.55, 83.59, etc.

In the above relations (1), (2), (3), (4), and (5), the value ranges off₁/f_(w), f₂/f_(w), f₁₁/f₁, f₁₂/f₁, and f₁₃/f₁ are closely related tosensitivities of a correction of system aberrations, a processingdifficulty of optical members, and assembly deviations of the opticalelements. The value of f₁/f_(w) in the relation (1) is less than −0.47,which improves the processability of the optical elements in the system.The value of f₂/f_(w) in the relation (2) is greater than −2.53, whichimproves the processability of the optical elements in the system, whileits value is less than −0.64, so that the system aberrations can befully corrected, thereby achieving higher quality optical effects. Thevalue of f₁₁/f₁ in the relation (3) is greater than 0.19, so that thesystem aberrations can be fully corrected, thereby achieving highquality optical effects. The value of f₁₃/f₁ in the relation (5) islarger than 0.019, so that the system aberrations can be fullycorrected, thereby achieving high quality optical effects. The value off₁₂/f₁ in the relation (4) is less than −0.019, which reduces difficultyof spherical aberration correction and facilitates realization of alarge optical aperture.

The first lens group includes four sub-lens groups, which arerespectively a first sub-lens group, a second sub-lens group, a thirdsub-lens group, and a fourth sub-lens group arranged adjacently. Thefirst sub-lens group, the second sub-lens group, and the third sub-lensgroup adopt a focal length combination of positive, negative, andpositive, and the focal length of the fourth lens group may be apositive focal length or a negative focal length, wherein the negativelens group corrects aberrations, and the positive lens group providesfocused imaging. The respective sub-lens groups adopt a focal lengthcombination of “positive, negative, positive, and positive” or“positive, negative, positive, and negative,” the combination of thesub-lens groups is relatively complex, which can further correctaberrations, and has better processability, thereby fully correcting theaberrations of the system, and improving the optical resolution of thesystem.

More importantly, with the transmission and reflection properties of thefirst optical element, the second optical element has a reflectionsurface to effectively fold the optical path, which reduces the overallsize of the eyepiece optical system, and improves the possibility ofsubsequent mass production. On the basis of miniaturization, cost andweight reduction for the article, the aberrations of the optical systemare greatly eliminated, and the basic optical indicators are alsoimproved to ensure high imaging quality and increase the size of thepicture angle. Therefore, an observer can watch large images of fullframe, high definition and uniform image quality without any distortionand get visual experience of high liveness via the present invention,and the present article is suitable for head-mounted near-to-eye displaydevices and similar devices.

In the above embodiment, the first optical element may be a polarizerwith 75% transmission and 25% reflection, or 65% transmission and 35%reflection, or a transflective function. The second optical element is acomponent only having a reflective function, which may be a lens or ametal piece with a reflective function.

As shown in FIG. 1 , a first optical element, a second optical element,and a first lens group arranged along an optical axis from a human eyeviewing side to a miniature image displayer are included. The opticalsurface closer to the eye E side is marked as 1, and by analogy (2, 3,4, 5, 6 . . . respectively from left to right). The light emitted fromthe miniature image displayer is refracted by the first lens group, andthen reflected on the first optical element to the second opticalelement. The light is reflected by the second optical element onto thefirst optical element, and then transmitted to the human eyes throughthe first optical element.

In a further embodiment, a distance along the optical axis between thefirst optical element and the second optical element is d₁, a distancealong the optical axis between the first optical element and the firstlens group is d₂, and d₁ and d₂ satisfy the following relation (6):0.82<d ₂ /d ₁  (6);

wherein, a value of d₂/d₁ may be 0.82, 0.83, 0.88, 0.98, 1.55, 2.37,3.55, 3.88, 3.99, 4.57, 4.89, 4.99, etc.

A lower limit of d₂/d₁ in the above relation (6) is greater than 0.82,which reduces the difficulty of correcting an off-axis aberration of thesystem, and ensures that both a central field-of-view and an edgefield-of-view achieve high image quality, so that the image quality inthe full frame is uniform.

In a further embodiment, a maximum effective optical aperture of thesecond optical element is φ₂, which satisfies following relation (7):φ₂<70 mm  (7);

wherein, a value of φ₂ may be 70, 69, 65, 56, 52, 48, 32, 30, 28, 26,21, etc., in mm.

In a further embodiment, the effective focal length f₁₁ of the firstsub-lens group, the effective focal length f₁₂ of the second sub-lensgroup, the effective focal length f₁₃ of the third sub-lens group, andthe effective focal length f₁ of the first lens group further satisfythe following relations (8), (9), and (10):0.78<f ₁₁ /f ₁<1.06  (8);−1.16<f ₁₂ /f ₁<−0.90  (9);1.38<f ₁₃ /f ₁<3.6  (10).

wherein, a value of f₁₁/f₁ may be 0.78, 0.79, 0.81, 0.83, 0.85, 0.895,0.954, 1.0, 1.05, 1,06, etc., a value of f₁₂/f₁ may be −1.16, −1.15,−1.12, −1.10, −1.07, −1.06, −1.03, −1.01, −0.95, −0.91, −0.90, etc., anda value of f₁₃/f₁ may be 1.38 1.39, 1.963, 2.19, 2.345, 2.548, 2.854,2.961, 3.54, 3.59, 3.6, etc.

By further optimizing the value ranges of the effective focal length ofthe first sub-lens group, the second sub-lens group, the third sub-lensgroup, and the system, the optical performance and difficulty ofprocessing and manufacturing of the optical system are better balanced.

In one of the embodiments, the first sub-lens group is composed of onelens; the first sub-lens group includes a first lens; and the first lensis a positive lens.

In one of the embodiments, the first sub-lens group is composed of twolenses, respectively a first lens distant from the miniature imagedisplayer side and a second lens proximate to the miniature imagedisplayer side; both the first lens and the second lens are positivelenses.

In a further embodiment, an effective focal length of the first lens isf₁₁₁, the effective focal length of the first sub-lens group is f₁₁, andf₁₁₁ and f₁₁, satisfy the following relation (11):0.10<|f ₁₁₁ /f ₁₁|  (1);

wherein, a value of |f₁₁₁/f₁₁| may be 0.10, 0.11, 0.22, 0.58, 1.32,1.55, 2.25, 3.57, 5.57, 8.79, 9.91, 10.11, 20.22, etc.

The value of |f₁₁₁/f₁₁| in the relation (11) is greater than 0.10, sothat the system aberrations can be fully corrected, thereby achievinghigh quality optical effects.

In a further embodiment, an optical surface of the first lens proximateto the human eye side is convex to the human eyes.

The above embodiment further eliminates system aberrations such asastigmatism and field curvature, which is beneficial to thehigh-resolution optical effect of the eyepiece system with uniform imagequality across the full frame.

In a further embodiment, the second sub-lens group is composed of onelens, and the second sub-lens group includes a third lens adjacent tothe first sub-lens group; the third lens is a negative lens; aneffective focal length of the third lens is f₁₂₁, and f₁₂₁ satisfies thefollowing relation (12):f ₁₂₁<−5.38  (12);

wherein, a value of f₁₂₁ may be −5.38, −5.39, −6.72, −9.88, −21.32,−41.55, −52.25, −63.57, −75.57, −88.79, −99.91, −110.11, −220.22, etc.The value of f₁₂₁ in the relation (12) is less than −5.38, which reducesthe difficulty of spherical aberrations correction and facilitates therealization of a large optical aperture.

In a further embodiment, the third sub-lens group is composed of onelens, and the third sub-lens group includes a fourth lens adjacent tothe second sub-lens group; the fourth lens is a positive lens; aneffective focal length of the fourth lens is f₁₃₁, and f₁₃₁ satisfiesthe following relation (13):8.82<f ₁₃₁  (13);

wherein, a value of f₁₃₁ may be 8.82, 8.83, 9.72, 19.88, 21.32, 41.55,52.25, 63.57, 75.57, 88.79, 99.91, 110.11, 220.22, etc. The value off₁₃₁ in the relation (13) is greater than 8.82, so that the systemaberrations can be fully corrected, thereby achieving high qualityoptical effects.

In a further embodiment, the fourth sub-lens group is composed of onelens, and the fourth sub-lens group includes a fifth lens adjacent tothe third sub-lens group; an optical surface of the fifth lens proximateto the miniature image displayer side is concave to the miniature imagedisplayer; an effective focal length of the fifth lens is f₁₄₁, and f₁₄₁satisfies the following relation (14):2.15<|f ₁₄₁ /f ₁|  (14):

wherein, a value of |f₁₄₁/f₁| may be 2.15, 2.16, 5.25, 8.1, 14.14,26.53, 48.78, 100, 225, etc. The value of |f₁₄₁/f₁| in the relation (14)is greater than 2.15, so that the system aberrations can be fullycorrected, thereby achieving high quality optical effects.

In a further embodiment, the fifth lens and the miniature imagedisplayer are movable together along the optical axis, for adjusting anequivalent visual virtual image distance of the eyepiece optical system.By moving image plane positions of the fifth lens and the miniatureimage displayer along the optical axis at the same time, the equivalentvisual virtual image distance of the eyepiece optical system may beadjusted.

In a further embodiment, the first lens group includes one or moreeven-order aspherical face shapes; two optical surfaces of the fifthlens are both even-order aspherical face shapes; and two opticalsurfaces of the second optical element are both even-order asphericalface shapes.

The aberrations at all levels of the optical system are furtheroptimized and corrected. The optical performance of the eyepiece opticalsystem is further improved.

In a further embodiment, the even-order aspherical face shape satisfiesthe following relation (15):

$\begin{matrix}{z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {\alpha_{2}r^{2}} + {\alpha_{4}r^{4}} + {\alpha_{6}r^{6}} + {\ldots.}}} & (15)\end{matrix}$

wherein, z is a vector height of the optical surface, c is a curvatureat the aspherical vertex, k is an aspherical coefficient, and α2, 4, 6 .. . are coefficients of various orders, and r is a distance coordinatefrom a point on a surface to an optical axis of a lens system.

The aberrations of the optical system (including spherical aberration,coma, distortion, field curvature, astigmatism, chromatic aberration andother higher-order aberrations) are fully corrected, which is beneficialfor the eyepiece optical system, while realizing a large angle of viewand a large aperture, to further improve the image quality of thecentral field-of-view and the edge field-of-view, and reduce the imagequality difference between the central field-of-view and the edgefield-of-view, thereby achieving more uniform image quality and lowdistortion in the full frame.

In a further embodiment, the first optical element is a planartransflective optical element; a reflectivity of the first opticalelement is Re₁, and Re₁ satisfies the following relation (16):20%<Re ₁<80%  (16);

wherein, a value of Re₁ may be 20%, 21%, 30%, 47%, 52%, 60%, 65%, 70%,79%, etc.

In a further embodiment, the second optical element includes two coaxialoptical surfaces of the same face shape.

In a further embodiment, a reflectivity of the optical reflectionsurface is Re₂, and Re₂ satisfies the following relation (17):20%<Re ₂  (17);

wherein, a value of Re₂ may be 20%, 21%, 30%, 47%, 52%, 60%, 65%, 70%,80%, 99%, etc.

In a further embodiment, an angle of optical axis between the first lensgroup and the second optical element is λ₁, and λ₁ satisfies thefollowing relation (18):55°<λ₁<120°  (18);

wherein, a value of λ₁ may be 55°, 60°, 66°, 70°, 90°, 100°, 115°, 120°,etc.

In one of the embodiments, the eyepiece optical system further includesa planar reflective optical element located between the first lens groupand the first optical element; the planar reflective optical elementreflects the image light refracted by the first lens group to the firstoptical element, the first optical element reflects the image light tothe second optical element, and then transmits the image light reflectedby the second optical element to the human eyes.

An included angle between the first lens group and the first opticalelement is λ₂, and λ₂ satisfies the following relation (19):60°≤λ₂≤180°  (19);

wherein, a value of λ₂ may be 60°, 74°, 80°, 90°, 100°, 130°, 140°,155°, 167°, 180°, etc.

In a further embodiment, the material of the second optical element isan optical plastic material, such as E48R, EP5000, and OKP1.

The aberrations at all levels of the eyepiece optical system are fullycorrected, and the manufacturing cost of the optical element and theweight of the optical system are also controlled.

The principles, solutions and display results of the above eyepieceoptical system will be further described below through more specificembodiments.

In the following examples, a diaphragm E may be the exit pupil ofimaging for the eyepiece optical system, which is a virtual light exitaperture. When the pupils of the human eyes are at the diaphragmposition, the best imaging effect can be observed. The spot diagramprovided in the following embodiment reflects a geometric structure ofthe imaging of the optical system, ignores the diffraction effect, andis represented by defocused spots formed by the cross-section of thefocused image plane with the specified field-of-view and the light ofthe specified wavelength, which can include multiple fields-of-view andlight of multiple wavelengths at the same time. Therefore, the qualityof the imaging quality of the optical system can be directly measured bythe density, shape, and size of the defocused spots of the spot diagram,and the chromatic aberration of the optical system can be directlymeasured by the dislocation degree of the defocused spots with differentwavelengths of the spot diagram. A smaller Root Mean Square (RMS) radiusof the spot diagram results in a higher imaging quality of the opticalsystem.

Example 1

The eyepiece design data of Example 1 is shown below in Table 1:

TABLE 1 Curvature Lens Net radius Thickness Refractive Abbe apertureCone Surface (mm) (mm) index number (mm) coefficient Diaphragm Infinite47 29.7581 2 −36.81803 −20 reflection 51.28161 −13.19062 3 Infinite 7reflection 32.81093 4 Infinite 15.78959 20.65268 5 26.76817 9.275991.80999 41.000073 12.15226 −19.5057 6 −17.55049 0.1981692 12.94693−2.225001 7 −29.56277 0.9965745 1.9459 17.943914 12.3449 2.331101 833.14961 0.8863538 12.35304 3.248082 9 22.85891 3.419771 1.8838537.205485 14.56063 −0.2472449 10 57.92243 6.106694 14.98012 44.87605 1115.98515 3.31471 1.757 47.713789 22.14129 12 21.70984 9.626206 21.33715Image plane Infinite 21.44313

FIG. 1 is an optical path diagram of an eyepiece optical systemaccording to Example 1, including: a first optical element L1 and asecondi optical element T2 arranged successively in an incidentdirection of an optical axis of human eyes, and a first lens group T1located on an optical axis of a miniature image displayer IMG. The firstoptical element L1 has optical performance of transmission andreflection at the same time. The first optical element L1 is used fortransmitting and reflecting an image light from the miniature imagedisplayer IMG. The second optical element T2 includes an opticalreflection surface L2, and the optical reflection surface L2 is concaveto a human eye EYE viewing direction. The first optical element L1reflects the image light refracted by the first lens group T1 to thesecond optical element T2, and then transmits the image light reflectedby the second optical element T2 to the human eyes EYE.

An effective focal length f_(w) of the eyepiece optical system is−26.08, an effective focal length f₁ of the first lens group T1 is12.52, and an effective focal length f₂ of the second optical element T2is 20.49. A distance d₁ along the optical axis between the first opticalelement L1 and the second optical element T2 is 20, and a distance d₂along the optical axis between the first optical element L1 and thefirst lens group T1 is 32.07. The first lens group T1 includes a firstsub-lens group T11, a second sub-lens group T12, a third sub-lens groupT3, and a fourth sub-lens group T14. The first sub-lens group T11 iscomposed of a positive lens, which is a first lens T111, and aneffective focal length f₁₁ of the first sub-lens group T111 is 9.95. Thesecond sub-lens group T12 is composed of a negative lens, which is athird lens T121. The third sub-lens group T13 is composed of a positivelens, which is a fourth lens T131. The fourth sub-lens group T14 iscomposed of a fifth lens T141. An effective focal length f₁₂ of thesecond sub-lens group T12 is −11.37, an effective focal length f₁₁₁ ofthe first lens T111 is 9.95, an effective focal length f₁₃ of the thirdsub-lens group T13 is 19.33, and an effective focal length f₁₄ of thefourth sub-lens group T14 is 64.06. Then, f₁/f_(w) is −0.48, f₂/f_(w) is−0.78, f₁₁/f₁ is 0.79, f₁₁₁/f₁₁ is 1, f₁₂/f₁ is −0.91, f₁₃/f₁ is 1.54,f₁₄/f₁ is 5.12, f₁₂₁ is −11.37, d₂/d₁ is 1.54, and λ₁ is 72°.

FIG. 2 , FIG. 3 a , FIG. 3 b , and FIG. 4 are respectively the spotdiagram, the field curvature diagram, the distortion diagram, and thetransfer function MTF plot, reflecting that respective field-of-viewlight in this example has high resolution and small optical distortionin the unit pixel of the image plane (miniature image displayer (IMG)).The resolution per 10 mm per unit period reaches more than 0.9. Theaberrations of the optical system and image drift are well corrected,and a display portrait of uniformity and high optical performance can beobserved through the eyepiece optical system.

Example 2

The eyepiece design data of Example 2 is shown below in Table 2:

TABLE 2 Curvature Lens Net radius Thickness Refractive Abbe apertureCone Surface (mm) (mm) index number (mm) coefficient Diaphragm Infinite37 5 2 −31.66126 −15 reflecfion 32.6238 −4.4437 3 Infinite 25.4579reflection 21.42564 4 58.09021 9.001287 1.713 53.868142 6.763383−50.0002 5 −12.14766 0.1999881 8.359922 −11.32412 6 −22.55956 4.2603671.8081 22.690566 8.365119 −50.00108 7 96.63623 0.6934065 9.48335841.8529 8 −979.1421 2.524395 1.7725 49.613485 9.660126 49.35443 9−11.52598 0.4986225 10.30524 10 8.684021 4.799284 1.61309 60.38371911.72043 11 9.906463 8.335471 9.94818 Image Infinite 9.54541 plane

FIG. 5 is an optical path diagram of an eyepiece optical systemaccording to Example 2, including: a first optical element L1 and asecond optical element T2 arranged successively in an incident directionof an optical axis of human eyes, and a first lens group T1 located onan optical axis of a miniature image displayer IMG. The first opticalelement L1 has optical performance of transmission and reflection at thesame time. The first optical element L1 is used for transmitting andreflecting an image light from the miniature image displayer IMG. Thesecond optical element T2 includes an optical reflection surface L2, andthe optical reflection surface L2 is concave to a human eye EYE viewingdirection. The first optical element L1 reflects the image lightrefracted by the first lens group T1 to the second optical element T2,and then transmits the image light reflected by the second opticalelement T2 to the human eyes EYE.

An effective focal length f_(w) of the eyepiece optical system is−11.49, an effective focal length f₁ of the first lens group T1 is 9.73,and an effective focal length f₂ of the second optical element T2 is7.47. A distance d₁ along the optical axis between the first opticalelement L1 and the second optical element T2 is 17, and a distance d₂along the optical axis between the first optical element L1 and thefirst lens group T1 is 23.46. The first lens group T1 includes a firstsub-lens group T11, a second sub-lens group T12, a third sub-lens groupT13, and a fourth sub-lens group T14. The first sub-lens group T11 iscomposed of a positive lens, which is a first lens T111, and aneffective focal length f₁₁ of the first sub-lens group T11 is 10.18. Thesecond sub-lens group T12 is composed of a negative les, which is athird lens T121. The third sub-lens group T13 is composed of positivelens, which is a fourth tens T131. The fourth sub-lens group T14 iscomposed of a fifth lens T141. An effective focal length f₁₂ of thesecond sub-lens group T12 is −5.39, an effective focal length f₁₃ of thethird sub-lens group T13 is 8.83; and an effective focal length f₁₄ ofthe fourth sub-lens group T14 is 21.02. Then, f₁/f_(w) is −0.85,f₂/f_(w), is −0.65, f₁₁/f₁ is 1.05, f₁₁₁/f₁₁ is 1, f₁₂/f₁ is −0.55,f₁₃/f₁ is 0.908, f₁₄/f₁ is 2.16, f₁₂₁ is −5.39, d₂/d₁ is 1.39, and λ₁ is70°.

FIG. 6 , FIG. 7 a , FIG. 7 b , and FIG. 8 are respectively the spotdiagram, the field curvature diagram, the distortion diagram, and thetransfer function MTF plot, reflecting that respective field-of-viewlight in this example has high resolution and small optical distortionin the unit pixel of the image plane (miniature image displayer (IMG)).The resolution per 10 mm per unit period reaches more than 0.9. Theaberrations of the optical system and image drift are well corrected,and a display portrait of uniformity and high optical performance can beobserved through the eyepiece optical system.

Example 3

The eyepiece design data of Example 3 is shown below in Table 3:

TABLE 3 Curvature Lens Net radius Thickness Refractive Abbe apertureCone Surface (max) (mm) index number (mm) coefficient Diaphragm Infinite48 5 2 −55.6533 −22.6 reflection 42.08992 −15.05038 3 Infinite 38.15881reflection 28.03543 4 Infinite 40 reflection 10.25769 5 −16.72401−2.960563 1.6938 53.151009 15.6 −1.219684 6 −55.52381 −2.738939 15.612.86236 7 −24.07627 −5.37627 1.58313 59.455980 16 −1.283208 8 14.63576−0.1686679 16 0.1537356 9 16.08364 −3.214711 1.6397 23.530454 15.2−3.587886 10 −65.66449 −8.000509 15.2 8.387683 11 −24.12175 −2.8459561.6584 50.866500 21 0.04313194 12 −59.55044 −3.411949 21 28.94518 13−18.80983 −4.565057 1.7725 49.613485 24 14 −19.86844 −7.549287 22 ImageInfinite 14.08951 plane

FIG. 9 a and FIG. 9 b are a front view and a top view of an optical pathstructure according to Example 3, including: a first optical element L1and a second optical element T2 arranged successively in an incidentdirection of an optical axis of human eyes, and a first lens group T1located on an optical axis of a miniature image displayer IMG, andfurther including a planar reflective optical element L3 located betweenthe first lens group and the first optical element. The first opticalelement L1 has optical performance of transmission and reflection at thesame time. The first optical element L1 is used for transmitting andreflecting an image light from the miniature image displayer IMG. Thesecond optical element T2 includes an optical reflection surface L2, andthe optical reflection surface L2 is concave to a human eye EYE viewingdirection. The planar reflective optical element L3 reflects the imagelight refracted by the first lens group T1 to the first optical elementL1, and the first optical element L1 reflects the image light to thesecond optical element T2, and then transmits the image light reflectedby the second optical element T2 to the human eyes EYE.

An effective focal length f_(w) of the eyepiece optical system is −16.8,an effective focal length f₁ of the first lens group T1 is 18.43, and aneffective focal length f₂ of the second optical element T2 is 27.83. Adistance d₁ along the optical axis between the first optical element L1and the second optical element T2 is 22.6, and a distance d₂ along theoptical axis between the first optical element L1 and the first lensgroup T1 is 48.16. The first lens group T1 includes a first sub-lensgroup T11, a second sub-lens group T12, a third sub-lens group T13, anda fourth sub-lens group T14. The first sub-lens group T11 is composed oftwo positive lenses, which are respectively a first lens T111 distantfrom the miniature image displayer IMG side and a second lens T112proximate to the miniature image displayer IMG side. An effective focallength f₁ of the first sub-lens group T11 is 12.94, and an effectivefocal length f₁₁₁ of the first lens T111 is 33.45. The second sub-lensgroup T12 is composed of one lens, which is a third lens T121. The thirdsub-lens group T13 is composed of a positive lens, which is a fourthlens T131. The fourth sub-lens group T14 is composed of a fifth lensT141. An effective focal length f₁₂ of the second sub-lens group T12 is−19.89, an effective focal length f₁₃ of the third sub-lens group T13 is59.67, and an effective focal length f₁₄ of the fourth sub-lens groupT14 is 158.7, wherein, d₂ consists of d₂₁ and d₂₂. Then, f₁/f_(w) is−1.1, f₂/f_(w) is −1.66, f₁₁/f₁ is 0.7, f₁₁₁/f₁₁ is 2.59, f₁₂/f₁ is−1.08, f₁₃/f₁ is 3.24, f₁₄/f₁ is 8.61, an effective focal length f₁₂₁ ofthe third lens T121 is −19.89, d₂/d₁ is 2.13, λ₁ is 72°, and λ₂ is 90°.

FIG. 10 , FIG. 11 a , FIG. 11 b , and FIG. 12 are respectively the spotdiagram, the field curvature diagram, the distortion diagram, and thetransfer function MTF plot, reflecting that respective field-of-viewlight in this example has high resolution and small optical distortionin the unit pixel of the image plane (miniature image displayer (IMG)).The resolution per 10 mm per unit period reaches more than 0.9. Theaberrations of the optical system and image drift are well corrected,and a display portrait of uniformity and high optical performance can beobserved through the eyepiece optical system.

Example 4

The eyepiece design data of Example 4 is shown below in Table 4:

TABLE 4 Curvature Lens Net radius Thickness Refractive Abbe apertureCone Surface (mm) (mm) index number (mm) coefficient Diaphragm Infinite47 5 2 −54.43931 −24 reflection 48.95158 −14.05856 3 Infinite 32.3114reflection 59.65487 4 Infinite −10 reflection 13.32531 5 −16.44166−2.618275 1.53116 56.043828 7.833633 −1.749706 6 −32.72957 −2.1523427.364828 −34.94002 7 −16.67698 −6.506248 1.651133 55.903805 8.317541−2.015585 8 15.67356 −0.2656935 8.599111 0.8499103 9 20.37391 −3.9648381.64219 22.408848 8.492684 −3.615109 10 −29.40104 −2.29513 9.577369−16.08668 11 −142.7324 −4.385973 1.72 50.351963 10.89104 −4.662146 1261.45032 −6.68695 12.29765 9.621991 13 −17.92474 −5 1.80999 41.00007316.57147 −6.966687 14 −19.54462 −6.85811 15.97538 −0.1664377 ImageInfinite 17.60037 plane

FIG. 13 a and FIG. 13 b are a front view and a top view of an opticalpath structure according to Example 4, including: a first opticalelement L1 and a second optical element T2 arranged successively in anincident direction of an optical axis of human eyes, and a first lensgroup T1 located on an optical axis of a miniature image displayer IMG,and further including a planar reflective optical element L3 locatedbetween the first lens group and the first optical element. The firstoptical element L1 has optical performance of transmission andreflection at the same time. The first optical element L1 is used fortransmitting and reflecting an image light from the miniature imagedisplayer IMG. The second optical element T2 includes an opticalreflection surface L2, and the optical reflection surface L2 is concaveto a human eye EYE viewing direction. The planar reflective opticalelement L3 reflects the image light refracted by the first lens group T1to the first optical element L1, and the first optical element L1reflects the image light to the second optical element T2, and thentransmits the image light reflected by the second optical element T2 tothe human eyes EYE.

An effective focal length f_(w) of the eyepiece optical system is −16.7,an effective focal length f₁ of the first lens group T1 is 16.76, and aneffective focal length f₂ of the second optical element T2 is 27.22. Adistance d₁ along the optical axis between the first optical element L1and the second optical element T2 is 24, and a distance d₂ along theoptical axis between the first optical element L1 and the first lensgroup T1 is 42.31. The first lens group T1 includes a first sub-lensgroup T11, a second sub-lens group T12, a third sub-lens group T13, anda fourth sub-lens group T14. The first sub-lens group T11 is composed oftwo positive lenses, which are respectively a first lens T111 distantfrom the miniature image displayer IMG side and a second lens T112proximate to the miniature image displayer IMG side. An effective focallength f₁₁ of the first sub-lens group T11 is 12.26, and an effectivefocal length f₁₁₁ of the first lens T111 is 58.91. The second sub-lensgroup T12 is composed of a negative lens, which is a third lens T121.The third sub-lens group T13 is composed of a positive lens, which is afourth lens T131. The fourth sub-lens group T14 is composed of a fifthlens T141. An effective focal length f₁₂ of the second sub-lens groupT12 is −18.17, an effective focal length f₁₃ of the third sub-lens groupT13 is 60.2, and an effective focal length f₁₄ of the fourth sub-lensgroup T14 is 112.12, wherein, d₂ consists of d₂₁ and d₂₂. Then, f₁/f_(w)is −1.0, f₂/f_(w) is −1.63, f₁₁/f₁ is 0.73, f₁₁₁/f₁₁ is 4.81, f₁₂/f₁ is−1.08, f₁₃/f₁ is 3.59, f₁₄/f₁ is 6.69, an effective focal length f₁₂₁ ofthe third lens T121 is −18.17, d₂/d₁ is 1.76, λ₁ is 74°, and λ₂ is 90°.

FIG. 14 , FIG. 15 a , FIG. 15 b , and FIG. 16 are respectively the spotdiagram, the field curvature diagram, the distortion diagram, and thetransfer function MTF plot, reflecting that respective field-of-viewlight in this example has high resolution and small optical distortionin the unit pixel of the image plane (miniature image displayer (IMG)).The resolution per 10 mm per unit period reaches more than 0.9. Theaberrations of the optical system and image drift are well corrected,and a display portrait of uniformity and high optical performance can beobserved through the eyepiece optical system.

Example 5

The eyepiece design data of Example 5 is shown below in Table 5:

TABLE 5 Curvature Lens Net radius Thickness Refractive Abbe apertureCone Surface (mm) (mm) index number (mm) coefficient Diaphragm Infinite47.84238 5 2 −48.03538 −24 reflection 48.74504 −10.60062 3 Infinite 27reflection 58.43923 4 13.09922 2.315851 1.5311 56.043828 14.2 −1.7013075 25.99627 2.559584 14.2 −21.67233 6 15.43821 4.899347 1.65113 55.90380515.6 −2.535522 7 −16.5758 0.2107574 15.6 0.9678087 8 −17.55681 2.2012651.6421 22.408848 15.8 −4.956789 9 22.32125 2.069532 16.6 −14.55218 1018.17215 4.279806 1.72 50.351963 19.8 −6.615312 11 −56.13364 10.1033320.2 18.46187 12 15.51061 3.095794 1.80999 41.000073 22.6 −1.011432 1313.33294 3.131787 22.6 −0.9285377 Image Infinite 17.24 plane

FIG. 17 is an optical path diagram of an eyepiece optical systemaccording to Example 5, including: a first optical element L1 and asecond optical element T2 arranged successively in an incident directionof an optical axis of human eyes, and a first lens group T1 located onan optical axis of a miniature image displayer IMG. The first opticalelement L1 has optical performance of transmission and reflection at thesame time. The first, optical element L1 is used for transmitting andreflecting an image light from the miniature image displayer IMG. Thesecond optical element T2 includes an optical reflection surface L2, andthe optical reflection surface L2 is concave to a human eye EYE viewingdirection. The first optical element L1 reflects the image lightrefracted by the first lens group T1 to the second optical element T2,and then transmits the image light reflected by the second opticalelement T2 to the human eyes EYE. The optical path structure furtherincludes a planar reflective optical element L3 located between thefirst lens group T1 and the first optical element L1. The planarreflective optical element L3 reflects the image light refracted by thefirst lens group T1 to the first optical element L1, and the firstoptical element L1 reflects the image light to the second opticalelement T2, and then transmits the image light reflected by the secondoptical element T2 to the human eyes EYE.

An effective focal length f_(w) of the eyepiece optical system is−16.49, an effective focal length f₁ of the first lens group T1 is12.97, and an effective focal length f₂ of the second optical element T2is 24.11. A distance d₁ along the optical axis between the first opticalelement L1 and the second optical element T2 is 30, and a distance d₂along the optical axis between the first optical element L1 and thefirst lens group T1 is 21. The first lens group T1 includes a firstsub-lens group T11, a second sub-lens group T12, a third sub-lens groupT13, and a fourth sub-lens group T14. The first sub-lens group T11 iscomposed of two positive lenses, which are respectively a first lensT111 distant from the miniature image displayer IMG side and a secondlens T112 proximate to the miniature image displayer IMG side. Aneffective focal length f₁₁ of the first sub-lens group T11 is 11.56, andan effective focal length fit of the first lens T111 is 46.79. Thesecond sub-lens group T12 is composed of a negative lens, which is athird lens T121. The third sub-lens group T13 is composed of a positivelens, which is a fourth lens T131. The fourth sub-lens group T14 iscomposed of a fifth lens T141. An effective focal length f₁₂ of thesecond sub-lens group T12 is −14.98, an effective focal length f₁₃ ofthe third sub-lens group T13 is 19.54, and an effective focal length f₁₄of the fourth sub-lens group T14 is −322.30. Then, f₁/f_(w) is −0.79,f₂/f_(w) is −1.46, f₁₁/f₁ is 0.89, f₁₁₁/f₁₁ is 4.05, f₁₂/f₁ is −1.15,f₁₃/f₁ is 1.51, f₁₄/f₁ is −24.85, an effective focal length f₁₂₁ of thethird lens T121 is −14.98, d₂/d₁ is 0.70, and λ₁ is 74°.

FIG. 18 , FIG. 19 a , FIG. 19 b , and FIG. 20 are respectively the spotdiagram, the field curvature diagram, the distortion diagram, and thetransfer function MTF plot, reflecting that respective field-of-viewlight in this example has high resolution and small optical distortionin the unit pixel of the image plane (miniature image displayer (IMG)).The resolution per 10 mm per unit period reaches more than 0.9. Theaberrations of the optical system and image drift are well corrected,and a display portrait of uniformity and high optical performance can beobserved through the eyepiece optical system.

The data of the above first to fifth examples all meet parameterrequirements recorded in the Summary of the invention, and results areshown in the following Table 6:

TABLE 6 f₁/f_(w) f₂/f_(w) f₁₁/f₁ f₁₁₁/f₁₁ f₁₂/f₁ f₁₃/f₁ Example 1 −0.48−0.78 0.79 1 −0.91 1.54 Example 2 −0.85 −0.65 1.05 1 −0.55 1.39 Example3 −1.1 −1.66 0.7 2.59 −1.08 3.24 Example 4 −1.0 −1.63 0.73 4.81 −1.083.59 Example 5 −0.79 −1.46 0.89 4.05 −1.15 1.51

The present application provides a head-mounted near-to-eye displaydevice, including a miniature image displayer, and further including thereflective eyepiece optical system according to any one of the aboveitems; the eyepiece optical system is located between the human eyes andthe miniature image displayer.

Preferably, the miniature image display is an organic electroluminescentdevice.

Preferably, the head-mounted near-to-eye display device includes twoidentical reflective eyepiece optical systems.

To sum up, the first lens group of the reflective eyepiece opticalsystem in the above examples of the present invention includes foursub-lens groups, which are the first sub-lens group, the second sub-lensgroup, the third sub-lens group, and the fourth sub-lens group,respectively. The first sub-lens group, the second sub-lens group, thethird sub-lens group, and the fourth sub-lens group adopt a specificfocal length combination, which fully corrects the aberrations of thesystem and improves the optical resolution of the system. Moreimportantly, with the transmission and reflection properties of thefirst optical element, the second optical element has a reflectionsurface, which effectively folds the optical path, reduces the overallsize of the eyepiece optical system, and improves the possibility ofsubsequent mass production. On the basis of miniaturization, cost andweight reduction for the article, the aberrations of the optical systemare greatly eliminated, and the basic optical indicators are alsoimproved, ensuring high image quality and increasing the size of thepicture angle. Therefore, an observer can watch large images of fullframe, high definition and uniform image quality without any distortionand get visual experience of high liveness via the present invention,which is suitable for head-mounted near-to-eye display devices andsimilar devices thereof.

It should be understood that, for one of ordinary skill in the art, theforegoing description can be modified or altered, and all suchmodifications and alterations fall into the scope of the attached claimsof the present invention.

What is claimed is:
 1. A reflective eyepiece optical system, composed ofa first optical element and a second optical element arrangedsuccessively in an incident direction of an optical axis of human eyes,and a first lens group located on an optical axis of a miniature imagedisplayer; wherein the first optical element is used for transmittingand reflecting an image light from the miniature image displayer; thesecond optical element comprises an optical reflection surface, and theoptical reflection surface is concave to the human eyes; the firstoptical element reflects the image light refracted by the first lensgroup to the second optical element, and then transmits the image lightreflected by the second optical element to the human eyes; an effectivefocal length of the eyepiece optical system is f_(w), an effective focallength of the first lens group is f₁, an effective focal length of thesecond optical element is f₂, and f_(w), f₁, and f₂ satisfy thefollowing relations (1) and (2):f ₁ /f _(w)<−0.47  (1);−2.53<f ₂ /f _(w)<−0.64  (2); the first lens group comprises a firstsub-lens group, a second sub-lens group, a third sub-lens group, and afourth sub-lens group arranged coaxially and successively along theoptical axis from a human eye viewing side to the miniature imagedisplayer side; effective focal lengths of the first sub-lens group, thesecond sub-lens group, and the third sub-lens group are a combination ofpositive, negative and positive; the effective focal length of the firstsub-lens group is f₁₁, the effective focal length of the second sub-lensgroup is f₁₂, the effective focal length of the third sub-lens group isf₁₃, and f₁₁, f₁₂, f₁₃, and f₁ satisfy the following relations (3), (4),and (5):0.19<f ₁₁ /f ₁  (3);f ₁₂ /f ₁<−0.019  (4);0.19 f ₁₃ /f ₁  (5).
 2. The reflective eyepiece optical system accordingto claim 1, wherein a distance along the optical axis between an opticalsurface of the first optical element distant from the human eye viewingside and the optical reflection surface of the second optical element isd₁, a distance along the optical axis between the optical surface of thefirst optical element distant from the human eye viewing side and anoptical surface in the first lens group closest to the human eye viewingside is d₂, and d₁ and d₂ satisfy the following relation (6):0.82 d ₂ d ₁  (6).
 3. The reflective eyepiece optical system accordingto claim 1, wherein a maximum effective optical aperture of the secondoptical element is φ₂, which satisfies the following relation (7):φ₂<70 mm  (7).
 4. The reflective eyepiece optical system according toclaim 1, wherein the effective focal length f₁₁ of the first sub-lensgroup, the effective focal length f₁₂ of the second sub-lens group, theeffective focal length f₁₃ of the third sub-lens group, and theeffective focal length f₁ of the first lens group further satisfy thefollowing relations (8), (9), and (10):0.78<f ₁₁ /f ₁<1.06  (8);−1.16<f ₁₂ /f ₁<−0.90  (9);1.38 f ₁₃ /f ₁<3.6  (10).
 5. The reflective eyepiece optical systemaccording to claim 1, wherein the first sub-lens group is composed oftwo lenses, which are respectively a first lens distant from theminiature image displayer side and a second lens proximate to theminiature image displayer side; both the first lens and the second lensare positive lenses.
 6. The reflective eyepiece optical system accordingto claim 1, wherein the second sub-lens group is composed of one lens,and the second sub-lens group comprises a third lens adjacent to thefirst sub-lens group; the third lens is a negative lens; an effectivefocal length of the third lens is f₁₂₁, and f₁₂₁ satisfies the followingrelation (12):f ₁₂₁<−5.38  (12).
 7. The reflective eyepiece optical system accordingto claim 1, wherein the third sub-lens group is composed of one lens,and the third sub-lens group comprises a fourth lens adjacent to thesecond sub-lens group; the fourth lens is a positive lens; an effectivefocal length of the fourth lens is f₁₃₁, and f₁₃₁ satisfies thefollowing relation (13):8.82<f ₁₃₁  (13).
 8. The reflective eyepiece optical system according toclaim 1, wherein the first optical element is a planar transflectiveoptical element; a reflectivity of the first optical element is Re₁, andRe₁ satisfies the following relation (16):20%<Re ₁<80%  (16).
 9. The reflective eyepiece optical system accordingto claim 1, wherein the second optical element comprises two coaxialoptical surfaces of the same face shape.
 10. The reflective eyepieceoptical system according to claim 1, wherein a reflectivity of theoptical reflection surface is Re₂, and Re₂ satisfies the followingrelation (17):20%<Re ₂  (17).
 11. The reflective eyepiece optical system according toclaim 1, wherein an angle of optical axis between the first lens groupand the second optical element is λ₁, and λ₁ satisfies the followingrelation (18):55°<λ₁<120°  (18).
 12. The reflective eyepiece optical system accordingto claim 1, wherein the eyepiece optical system further comprises aplanar reflective optical element located between the first lens groupand the first optical element; the planar reflective optical elementreflects the image light refracted by the first lens group to the firstoptical element, the first optical element reflects the image light tothe second optical element, and then transmits the image light reflectedby the second optical element to the human eyes; an angle of opticalaxis between the first lens group and the first optical element is λ₂,and λ₂ satisfies the following relation (19):60°≤λ₂≤180°  (19).
 13. The reflective eyepiece optical system accordingto claim 1, wherein the material of the second optical element is anoptical plastic material.
 14. A head-mounted near-to-eye display device,comprising a miniature image displayer, and further comprising thereflective eyepiece optical system according to claim 1; wherein theeyepiece optical system is located between the human eyes and theminiature image displayer.
 15. The reflective eyepiece optical systemaccording to claim 1, wherein the first sub-lens group is composed ofone lens; the first sub-lens group comprises a first lens; and the firstlens is a positive lens.
 16. The reflective eyepiece optical systemaccording to claim 15, wherein an effective focal length of the firstlens is f₁₁₁, the effective focal length of the first sub-lens group isf₁₁, and f₁₁₁ and f₁₁ satisfy the following relation (11),0.10<|f ₁₁₁ /f ₁₁|  (1).
 17. The reflective eyepiece optical systemaccording to claim 15, wherein an optical surface of the first lensproximate to the human eye side is convex to the human eyes.
 18. Thereflective eyepiece optical system according to claim 1, wherein thefourth sub-lens group is composed of one lens, and the fourth sub-lensgroup comprises a fifth lens adjacent to the third sub-lens group; anoptical surface of the fifth lens proximate to the miniature imagedisplayer side is concave to the miniature image displayer; an effectivefocal length of the fifth lens is f₁₄₁, and f₁₄₁ satisfies the followingrelation (14):2.15<|f ₁₄₁ /f ₁|  (14).
 19. The reflective eyepiece optical systemaccording to claim 18, wherein the fifth lens and the miniature imagedisplayer are movable together along the optical axis, for adjusting anequivalent visual virtual image distance of the eyepiece optical system.20. The reflective eyepiece optical system according to claim 18,wherein the first lens group comprises one or more even-order asphericalface shapes; two optical surfaces of the fifth lens are both even-orderaspherical face shapes; and two optical surfaces of the second opticalelement are both even-order aspherical face shapes.